1. Field of the Invention
The present invention relates to an image processing apparatus such as an MFP (Multi Function Peripherals) that is a multifunctional digital image forming apparatus, an image processing method employed by the apparatus, and a non-transitory recording medium storing a computer readable image processing program.
2. Description of the Related Art
When image data is to be input from a device such as a high-speed scanner device included in an image processing apparatus that cannot be stopped in the middle once an image starts to be input, it is required that a region be provided to retain a single page of raw data or compressed encoded data in order to ensure that a single page's worth of the image data is input.
A memory incorporated in the image processing apparatus includes a main memory which is disposed to be freely accessed from a CPU and be expanded as needed, and a sub-memory which can be accessed via DMA (Direct Memory Access) transfer only and has the size just enough for the device configuration. There is also required an auxiliary storage device which holds a large amount of encoded data.
Cost-wise, the main memory configured to be expanded as needed is more expensive than the sub-memory. Moreover, the main memory and the sub-memory need to be disposed to be accessed in separate channels in order to secure the band required for image transfer.
When the input of the single page's worth of image data is ensured by the main memory, the image can be input at high speed by using an automatic original feeding unit mounted to the scanner device. The number of pages securely input to achieve the maximum input speed varies depending on the configuration of the automatic original feeding unit but, in general, the input speed can be increased by using more memory.
Some image processing apparatuses including an automatic original feeding unit with a dual scan technique are configured to be able to save image data worth four pages of A3-sized originals at once into the main memory, for example. An image processing apparatus including a normal automatic original feeding unit is often configured to be able to save two pages' worth of image data at once into the main memory.
The automatic original feeding unit can read the original at high speed since a memory area provided to save the image can be secured one after another in the main memory.
On the other hand, the size of the expensive main memory needs to be decreased in order to provide a low-speed, inexpensive image processing apparatus. Accordingly, the main memory can be adapted to save the image data worth a single page of the A3-sized original in order to be provided in the minimum size. When the main memory is adapted to hold the image data worth the single page of the original input from the scanner device, the image data of a next original cannot be input until after the image data being held is saved in the auxiliary storage device such as a hard disk device. Moreover, the image data for output cannot be read from the auxiliary storage device while the image data is being input, whereby the performance is notably degraded.
Accordingly, the less expensive sub-memory is provided with a buffer per page to save the encoded data per band successively into the auxiliary storage device, so that the input of the next image data can be started right after completing the input of the current image data. Moreover, the memory area in the main memory is not used extensively when inputting the image data, so that the image data can be output while the image data is being input and that the efficiency is improved.
As described above, each of the inexpensive image processing apparatus and the image processing apparatus equipped with the sufficient main memory and supporting high-speed image input has its own method of inputting the image data suitable for each apparatus, and thus also differs in the size of the memory area to be secured in the main memory and the sub-memory.
Therefore, the image processing apparatus in the manufacturing process thereof is equipped with the sub-memory and the main memory each having the memory size large enough to be able to secure the required memory area, in accordance with the characteristic of the image processing apparatus. When inputting the image data from the scanner device, a control unit of the image processing apparatus secures the memory area in each of the sub-memory and the main memory and performs input processing of the image data where, in the related art, such control unit has been configured individually for each image processing apparatus to perform the intended input processing of the image data.
Note that JP 2006-20029 A discloses an image input/output apparatus in which, when an image output unit cannot be stopped once started up, a code memory secures the memory capacity large enough to accommodate all data corresponding to pages being output while a bit map memory secures a memory size per band less than a page and, when the image output unit is not the output unit that cannot be stopped once started up, both the code memory and a second bit map memory are secured per band.
However, the control unit cannot be standardized where the control unit of the image processing apparatus is configured individually for each image processing apparatus to perform the intended input processing of the image data as described above, thereby causing an increase in cost.
Note that the technique described in JP 2006-20029 A does not disclose anything related to the standardization of the control unit pertaining to the input processing of the image data using the sub-memory and the main memory and thus does not provide a solution to the aforementioned problem.